Use a Browser on your computer to log in to your google account.
Then check which devices are connected, disconnect all mobile devices and try again.
A also recommend to change you password.
This is the alread well known chinese LRTWRP recovery and described here
https://xiaomi.eu/community/threads/twrp-for-xiaomi-redmi-note-9s-pro-wzsx150.55618/
Install activity launcher e.g. from here
https://m.apkpure.com/activity-launcher/de.szalkowski.activitylauncher
and create shortcut for:
Google Play Store
or
com.android.vending.AssetBrowserActivity
There is a generic user guide on top of this page.
https://i01.appmifile.com/webfile/globalimg/Global_UG/Mi_Smartphone/User_Guide/mi_phone_user_manual_EN.pdf